1. Field of the Invention
The present invention relates to drug-eluting medical devices; more particularly, this invention relates to processes for controlling the interaction among polymer, drug and solvent, and the release rate of a drug for drug eluting medical devices.
2. Background of the Invention
Strict pharmacological and good mechanical integrity of a drug eluting medical device are required to assure a controlled drug release. Significant technical challenges exist when developing an effective and versatile coating for a drug eluting medical device, such as a stent.
A coating may be applied by a spray coating process. A drug-polymer composition dissolved in a solvent is applied to the surface of a medical device using this method. The amount of drug-polymer to be applied has been expressed as a target coating weight, which corresponds to the weight of the coating after a substantial amount of the solvent has been removed.
It is desirable to obtain better control over the drug-eluting product. Specifically, there is a need to better control the rate of release of a drug, or the effectiveness of a drug when released from the coating. To date the known prior art has failed to provide adequate solutions.